Hopefully this is a quick fix..but basically i hooked up a 4 channel amp and a 1 channel..(for my sub). All 4 speakers are wired into the 4 channel which includes a pair of coaxials in the extra cab part..and seperates/tweeters in the doors in the front...with a crossover. Doesn't seem to effect the sound quality at all but its kind of annoying at low volume as it seems to sometimes overtake the speaker sound.

1. turn the gains on the amps (gain is only in the amps, some headunits now offer "level adjustment" type of thing for adjusting levels between sources - set these to 0 for now - then adjust after to avoid dramatic volume changes when going from source to source). To turn the gain down.. turn it all the way left.

2. find a really well recorded, clean sounding (no distortion/overloading recorded right into the song) song/songs on cd (originals are best) if not - on your ipod - Madonna, MJ, Jazz etc usually are safe if your not sure

2.5 - turn off loudness on your deck, set EQ's etc to 0 or Flat

3. If you can find the clipping level of your headunit - turn it up to that - if not go to about 3/4 or 7/8s of the volume while playing those discs - if you want to know about clipping as again later and if I have time I will explain

4. now on your speaker amp - slowly turn the gain up until you either - get too loud to listen to, or until you start to hear the music distorting slightly - usually you will hear the change in how guitars, cymbals and female vocals - the start to sound brittle or compressed

5. now back off the gain a hair.

6. do the same for the subs - using clean sounding bass - it's easy to hear when bass distorts - use a song with a consistant bass track makes it easier.

7. ok, so now you have a little extra on the volume on the deck for songs/discs that are recorded lower or when you really want that extra bit to go to "11"

That is a quick summary of how to set gains.. a bit rushed but you get the idea.

Avoid using a ton of bass boost etc on the headunit now..

Let us know how that goes.. should solve the ish and get things sounding better.

Oh one note.. in a perfect world you would leave the gains/system at a point where it would not clip, but most of us don't have the power for that (to get it "loud") and for alot of people a system doesn't sound "loud enough" unless they can hear distortion.

A perfect system would be a headunit that does not clip at all, and amps set to just clip or not clip at all.

You link showed a Single voice coil sub and a mono amp.. so just positive on sub to Positive Speaker terminal on amp, and neg on sub to neg speaker output on the amp. If you sub is a Dual Voice Coil, I would need to verify the impedence of each coil, but they are usually 4 ohm each coil, just just hook all the pos up and the neg up to get to a 2 ohm load.. which the amp you should is stable to from the info there.

Now if your sub is a single VC (which your link showed) it's a 4 ohm sub - that can handle 400W RMS.. the amp you showed is rated to do 425 RMS.. so it is a nice match.

Should be no problems if you don't overgain the system, or over boost it.. or just plain overdrive it. If you are.. put in a bigger or more subs and more power

Good news.. you now bump up in power from the amp - I think it's about 700 if I remember..

So now.. go from the pos speaker out on the amp to both + terminals on the sub. and from the neg speaker out to both - terminals on the sub (this is called parallel wiring) you dont need to run 2 wires on each run, just 1 to the first term on the sub then jump from the 1st to the second.